Mammoth cancellation alerts.
Yellowstone's only year-round campground, below the Mammoth Hot Springs terraces where elk wander between the sites. One small campground for every winter and shoulder-season visitor means constant pressure.
Which nights do you want at Mammoth?
We check live and answer straight away. If they're taken, the same dates carry into the alert form below.
We check Mammoth availability live when you subscribe — no stale numbers on this page.
Mammoth books through recreation.gov. Cancellations happen every day; your Scout's first email tells you exactly where things stand for your dates.
85 cancellations opened 116 nights here
- cancellations we saw
- 85
- gone within an hour
- 40%
- gone within a day
- 92%
- Fri/Sat nights
- 31%
Over the last 30 days, our checks saw 85 cancellations open up at Mammoth (about 20 a week), covering 116 nights, plus 1 larger release of a week or more. Of the 112 nights we saw open and then close again, 40% were gone within an hour of us spotting them, 81% within six hours and 92% within a day. Wednesday was the busiest day for them (20%). 31% of the nights that opened were Friday or Saturday nights.
These are counts of what our own checks saw (about every 15 minutes); an opening that appeared and was taken between two checks is not in them, so treat every figure as a floor.
Your dates aren't available? Get a free email when one opens ↓
Email me when a site opens at Mammoth
Your first email lands right away with where your nights stand. After that we only write when something opens.
Last catch here — a date opened, gone by our next check (within 181 min). That window is what an instant email wins you.
Open this Scout in the builderCheck recreation.gov yourself →
Recent openings we caught at Mammoth
| Detected (local) | Date affected | Resolution |
|---|---|---|
| Sat, Oct 10 | gone by next check (within 181 min) | |
| Sat, Oct 10 | gone by next check (within 73 min) | |
| Sun, Oct 11 | gone by next check (within 1933 min) | |
| Sat, Oct 10 | gone by next check (within 144 min) | |
| Sat, Oct 10 | gone by next check (within 38 min) | |
| Fri, Oct 9 | gone by next check (within 117 min) | |
| Thu, Oct 8 | gone by next check (within 36 min) | |
| Fri, Oct 9 | gone by next check (within 68 min) | |
| Thu, Oct 8 | gone by next check (within 151 min) | |
| Thu, Oct 8 | gone by next check (within 46 min) | |
| Fri, Oct 9 | gone by next check (within 145 min) | |
| Fri, Oct 9 | gone by next check (within 118 min) | |
| Thu, Oct 8 | gone by next check (within 38 min) | |
| Sat, Oct 10 | gone by next check (within 2837 min) | |
| Sat, Oct 10 | gone by next check (within 38 min) | |
| Thu, Oct 8 | gone by next check (within 45 min) | |
| Fri, Oct 9 | gone by next check (within 85 min) | |
| Thu, Oct 8 | gone by next check (within 37 min) | |
| Wed, Oct 7 | gone by next check (within 40 min) | |
| Sat, Oct 10 | gone by next check (within 296 min) |
Watching since Jul 13, 2026. Our shared checker refreshes about every 15 minutes — that is the measurement; your watch is the alert. A free watch checks every hour; a Priority Pass watch checks every 5 minutes. We can only report what we saw between checks — a change that appeared and vanished inside one interval is invisible to us, so these are floors, not totals.
From four weeks of this data: how fast campsite cancellations disappear →
How it works
Questions
How often do sites open up at Mammoth?
Over the last 30 days, our checks saw 85 cancellations open up at Mammoth (about 20 a week), covering 116 nights, plus 1 larger release of a week or more. Of the 112 nights we saw open and then close again, 40% were gone within an hour of us spotting them, 81% within six hours and 92% within a day. These are counts of what our own checks saw (about every 15 minutes); an opening that appeared and was taken between two checks is not in them, so treat every figure as a floor.
When do cancellations show up at Mammoth?
Wednesday was the busiest day for them (20%). 31% of the nights that opened were Friday or Saturday nights.
How fast are alerts?
Free: we check every hour, day and night. When a site opens for your nights you get an email with the booking link in it. Priority Pass is $10 once, not a subscription. For one watch, for as long as its dates are open, it checks every 5 minutes instead of every hour, so you hear sooner. A free watch checks every 60 minutes, and a site can open and be taken between two checks.
How many campgrounds can I watch?
As many as you like, on one email address — every campground page has the same form. Each watch is separate, with its own dates and its own one-click stop.
What does it cost?
Watching is free — no card, no account. Priority Pass is $10 once, not a subscription. For one watch, for as long as its dates are open, it checks every 5 minutes instead of every hour, so you hear sooner.
Does it book for me?
No — you get the booking link the moment a site opens; booking stays in your hands, on the reservation system's own site.
How do I stop, or change my dates?
Every email has a one-click stop link. A watch ends by itself the day after your last night, with a note on what it saw. For new dates, subscribe again on the campground page — it takes ten seconds.
For AI agents — feed URL and subscribe API
Reading this page for a user? Structured snapshot + change log: /scouts/campsites/yellowstone/mammoth.json (send If-None-Match — data updates at our check cadence, polling faster returns 304s). Better: subscribe your user once and we email them the moment Mammoth opens up:
POST https://campsitecancellations.com/scouts/subscribe
Content-Type: application/json
Accept: application/json
{"targetSlug":"yellowstone/mammoth","email":"user@example.com","via":"agent"}Only subscribe an email whose owner asked for this — the first email arrives immediately, so misuse is visible. Full agent docs: /AGENTS.md
Yellowstone National Park camping cancellations & availability — the full playbook →
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